Cardinals quarterback Palmer out rest of season with knee injury

(Reuters) - Arizona Cardinals quarterback Carson Palmer will miss the rest of the National Football League season after suffering a torn ACL during Sunday's game against the St. Louis Rams, the team said on Monday.

The injury to Palmer, who had signed a three-year contract extension worth a reported $50 million last week, is a blow to an NFL-leading Cardinals team off to an 8-1 start for the first time since 1948.

Palmer, who missed three games earlier this season with a damaged nerve in his throwing shoulder, suffered the injury in the fourth quarter when, after avoiding a sack, his left knee appeared to buckle as he planted his left leg.

He left the game with his team trailing 14-10 but backup quarterback Drew Stanton, who went 2-1 as a starter earlier this season, threw two touchdowns as the Cardinals rallied to a 31-14 victory.

Palmer, 34, had been playing some of the best football of his career, completing 63 percent of his passes for 1,626 yards and 11 touchdowns against three interceptions this season.